U.S. patent number 6,181,998 [Application Number 09/223,719] was granted by the patent office on 2001-01-30 for start controlling method for a passenger protection system, start controlling system for a passenger protection system, and recording medium for recording a start controlling program for a passenger protection system.
This patent grant is currently assigned to Airbag Systems Co., Ltd.. Invention is credited to Yasumasa Kanameda, Koichi Miyaguchi.
United States Patent |
6,181,998 |
Kanameda , et al. |
January 30, 2001 |
**Please see images for:
( Certificate of Correction ) ** |
Start controlling method for a passenger protection system, start
controlling system for a passenger protection system, and recording
medium for recording a start controlling program for a passenger
protection system
Abstract
A start control system for a passenger protection system wherein
after a first inflator has been fired, a detected deceleration of
the vehicle is compared with a previously stored predetermined
deceleration. Next, time integration is executed over an area in
which the detected deceleration of the vehicle exceeds the
previously stored predetermined deceleration if it has been decided
that the detected deceleration of the vehicle exceeds the
previously stored predetermined deceleration to increase speed
reduction. Then, the time integral value is added to a speed
integral value which is calculated as time integration of the
detected deceleration of the vehicle until a point of time when it
has been decided that the detected deceleration of the vehicle
exceeds the previously stored predetermined deceleration. Finally,
a start signal for a second inflator is output by a CPU to fire the
second inflator when an added result exceeds a predetermined
threshold value. As a result, even if stagnation of the speed
integral value is caused, the second inflator can be fired without
fail.
Inventors: |
Kanameda; Yasumasa (Tomioka,
JP), Miyaguchi; Koichi (Tomioka, JP) |
Assignee: |
Airbag Systems Co., Ltd.
(Gunma, JP)
|
Family
ID: |
13975321 |
Appl.
No.: |
09/223,719 |
Filed: |
December 31, 1998 |
Foreign Application Priority Data
|
|
|
|
|
Mar 19, 1998 [JP] |
|
|
10-089602 |
|
Current U.S.
Class: |
701/45; 180/271;
180/282; 280/735; 307/10.1; 340/436; 340/669; 701/46 |
Current CPC
Class: |
B60R
21/0132 (20130101); B60R 21/0133 (20141201); B60R
21/01526 (20141001) |
Current International
Class: |
B60R
21/01 (20060101); G06F 007/00 (); G60R 022/00 ();
G05D 003/00 () |
Field of
Search: |
;701/45,36,46,47
;280/734,735,731,732,802,806 ;180/271,268,282 ;307/10.1
;340/436,669 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Louis-Jacques; Jacques H.
Attorney, Agent or Firm: Wenderoth, Lind & Ponack,
LLP.
Claims
What is claimed is:
1. A start controlling method for a passenger protection system,
for controlling start of the passenger protection system which has
a first inflator and a second inflator and is constructed such that
a protection system for protecting passengers of a vehicle is
started by firing the first inflator and the second inflator,
respectively, in response to a start signal from an external
device, said method comprising:
detecting a deceleration of a vehicle;
calculating a speed integral value which is a time integration of
the deceleration;
deciding whether or not the speed integral value exceeds a first
predetermined threshold value, and then starting the first inflator
if it has been decided that the speed integral value exceeds the
first predetermined threshold value;
comparing a detected deceleration of the vehicle with a previously
stored predetermined deceleration, wherein the previously stored
predetermined deceleration corresponds to a maximum deceleration
out of decelerations which are detected when firing of the first
inflator is needed and firing of the second inflator is not needed
and are detected from a fire time of the first inflator to a
desired fire time of the second inflator, for a first predetermined
time after the first inflator has been started, then deciding
whether or not the detected deceleration of the vehicle exceeds the
previously stored predetermined deceleration to increase speed
reduction, and then executing time integration over an area to
calculate a time integral value, in which the detected deceleration
of the vehicle exceeds the previously stored predetermined
deceleration, for a second predetermined time if it has been
decided that the detected deceleration of the vehicle exceeds the
previously stored predetermined deceleration to increase the speed
reduction;
adding the time integral value to a speed integral value which is
calculated as a time integration of the detected deceleration of
the vehicle until a point of time when it has been decided that the
detected deceleration of the vehicle exceeds the previously stored
predetermined deceleration to increase the speed reduction to
calculate an added result; and
deciding whether or not the added result exceeds a second
predetermined threshold value, and then executing start of the
second inflator if it has been decided that the added result
exceeds the second predetermined threshold value.
2. A start controlling system for a passenger protection system,
for controlling start of the passenger protection system which has
a first inflator and a second inflator and is constructed such that
a protection system for protecting passengers of a vehicle is
started by firing the first inflator and the second inflator,
respectively, in response to a start signal from an external
device, said system comprising:
a first integrating means for executing time integration with
respect to a deceleration of a vehicle input from an external
device;
a first integral value deciding means for deciding whether or not a
value calculated by said first integrating means exceeds a first
predetermined threshold value;
an acceleration deciding means for deciding whether or not the
deceleration of the vehicle input from the external device exceeds
a previously stored predetermined deceleration, wherein the
previously stored predetermined deceleration corresponds to a
maximum deceleration out of decelerations which are detected when
firing of the first inflator is needed and firing of the second
inflator is not needed and are detected from a fire time of the
first inflator to a desired fire time of the second inflator, after
a point of time when it is decided by said first integral value
deciding means that the value calculated by said first integrating
means exceeds the first predetermined threshold value;
a second integrating means for executing time integration over an
area, in which the deceleration of the vehicle input from the
external device exceeds the previously stored predetermined
deceleration, for a predetermined time after a point of time when
it has been decided that the deceleration of the vehicle input from
the external device exceeds the previously stored predetermined
deceleration;
an adding means for adding an integral value, which is calculated
by said first integrating means when it is decided by said
acceleration deciding means that the deceleration of the vehicle
input from the external device exceeds the previously stored
predetermined deceleration, to an integral value calculated by said
second integrating means;
a second integral value deciding means for deciding whether or not
a value calculated by said adding means exceeds a second
predetermined threshold value; and
a start signal outputting means for outputting a start signal for
the first inflator when it has been decided by said first integral
value deciding means that the value calculated by said first
integrating means exceeds the first predetermined threshold value,
and outputting a start signal for the second inflator when it has
been decided by said second integral value deciding means that the
value calculated by said adding means exceeds the second
predetermined threshold value.
3. A start controlling system for a passenger protection system,
for controlling start of the passenger protection system which has
a first inflator and a second inflator and is constructed such that
a protection system for protecting passengers of a vehicle is
started by firing the first inflator and the second inflator,
respectively, in response to a start signal from an external
device, said system comprising:
a central processing unit, based on a predetermined program loaded
from an external device, operable to:
execute time integration with respect to an externally input
deceleration of a vehicle,
decide whether or not a time integral value exceeds a first
predetermined threshold value, and then output a start signal for
the first inflator if it has been decided that the time integral
value exceeds the first predetermined threshold value,
compare a detected deceleration of the vehicle with a previously
stored predetermined deceleration, wherein the previously stored
predetermined deceleration corresponds to a maximum deceleration
out of decelerations which are detected when firing of the first
inflator is needed and firing of the second inflator is not needed
and are detected from a fire time of the first inflator to a
desired fire time of the second inflator, for a first predetermined
time after the first inflator has been started, then decide whether
or not the detected deceleration of the vehicle exceeds the
previously stored predetermined deceleration to increase speed
reduction, and then execute time integration over an area to
calculate a time integral value, in which the detected deceleration
of the vehicle exceeds the previously stored predetermined
deceleration, for a second predetermined time thereafter if it has
been decided that the detected deceleration of the vehicle exceeds
the previously stored predetermined deceleration to increase the
speed reduction,
add the time integral value to a speed integral value which is
calculated as time integration of the detected deceleration of the
vehicle until a point of time when it has been decided that the
detected deceleration of the vehicle exceeds the previously stored
predetermined deceleration to increase the speed reduction to
calculate an added result, and
decide whether or not the added result exceeds a second
predetermined threshold value, and then outputting a start signal
for the second inflator is it has been decided that the added
result exceeds the second predetermined threshold value;
a memory device operable to store the program, which is executed by
said central processing unit, to be readable by said central
processing unit;
a D/A converter operable to convert a digital start signal, which
is supplied from said central processing unit to the first inflator
and the second inflator, into an analog signal; and
an interface circuit operable to convert an output signal of said
D/A converter into predetermined signals which are suitable for the
first inflator and the second inflator, respectively.
4. A start controlling method for a passenger protection system,
for controlling start of lie passenger protection system which has
a first inflator and a second inflator and is constructed such that
a protection system for protecting passengers of a vehicle is
started by firing the first inflator and the second inflator,
respectively, in response to a start signal from an external
device, said method comprising:
detecting a deceleration of a vehicle;
calculating a speed integral value which is a time integration of
the deceleration;
deciding whether or not the speed integral value exceeds a
predetermined threshold value defined according to a detected
deceleration of the vehicle;
starting the first inflator if it has been decided that the speed
integral value exceeds the predetermined threshold value defined
according to the detected deceleration of the vehicle;
comparing the detected deceleration of the vehicle with a
previously stored predetermined deceleration, wherein the
previously stored predetermined deceleration corresponds to a
maximum deceleration out of decelerations which are detected when
firing of the first inflator is needed and firing of the second
inflator is not needed and are detected from a fire time of the
first inflator to a desired fire time of the second inflator, for a
predetermined time after the first inflator has been started, then
deciding whether or not the detected deceleration of the vehicle
exceeds the previously stored predetermined deceleration to
increase speed reduction;
holding a threshold value defined according to the deceleration
until termination of the predetermined time thereafter if it has
been decided that the detected deceleration of the vehicle exceeds
the previously stored predetermined deceleration to increase the
speed reduction, and then deciding whether or not the speed
integral value exceeds the predetermined threshold value being held
for that time duration; and
starting the second inflator if it has been decided that the speed
integral value exceeds the predetermined threshold value being
held.
5. A start controlling system for a passenger protection system,
for controlling start of the passenger protection system which has
a first inflator and a second inflator and is constructed such that
a protection system for protecting passengers of a vehicle is
started by firing the first inflator and the second inflator,
respectively, in response to a start signal from an external
device, said system comprising:
an integrating means for executing time integration with respect to
a deceleration of a vehicle input from an external device;
a first integral value deciding means for deciding whether or not a
value calculated by said integrating means exceeds a predetermined
threshold value defined according to the deceleration of the
vehicle;
an acceleration deciding means for deciding whether or not the
deceleration of the vehicle input from the external device exceeds
a previously stored predetermined deceleration, wherein the
previously stored predetermined deceleration corresponds to a
maximum deceleration out of decelerations which are detected when
firing of the first inflator is needed and firing of the second
inflator is not needed and are detected from a fire time of the
first inflator to a desired fire time of the second inflator, to
increase speed reduction, for a predetermined time after a point of
time when it is decided by said first integral value deciding means
that the value calculated by said integrating means exceeds the
predetermined threshold value defined according to the deceleration
of the vehicle;
a second integrating means for holding a threshold value defined
according to the deceleration of the vehicle until termination of
the predetermined time when it has been decided by said
acceleration deciding means that the deceleration of the vehicle
input from the external device exceeds the previously stored
predetermined deceleration to increase the speed reduction, and
then deciding whether or not a value calculated by said integrating
means exceeds the predetermined threshold value being held for this
time duration; and
a start signal outputting means for outputting a start signal for
the first inflator when is has been decided by said first integral
value deciding means that the value calculated by said first
integrating means exceeds the first predetermined threshold value,
and outputting a start signal for the second inflator when it has
been decided by said second integral value deciding means that the
value calculated by said integrating means exceeds the
predetermined threshold value being held.
6. A start controlling system for a passenger protection system,
for controlling start of the passenger protection system which has
a first inflator and a second inflator and is constructed such that
a protection system for protecting passengers of a vehicle is
started by firing the first inflator and the second inflator,
respectively, in response to a start signal from an external
device, the system comprising:
a central processing unit, based on a predetermined program loaded
from an external device, operable to:
execute time integration with respect to an externally input
deceleration of a vehicle,
decide whether or not a time integral value exceeds a predetermined
threshold value defined according to the externally input
deceleration of the vehicle,
output a start signal for the first inflator if it has been decided
that the time integral value exceeds a predetermined threshold
value defined according to a detected deceleration of the
vehicle,
compare the detected deceleration of the vehicle with a previously
stored predetermined deceleration, wherein the previously stored
predetermined deceleration corresponds to a maximum deceleration
out of decelerations which are detected when firing of the first
inflator is needed and firing of the second inflator is not needed
and are detected from a fire time of the first inflator to a
desired fire time of the second inflator, for a predetermined time
after the first inflator has been started, then decide whether or
not the detected deceleration of the vehicle exceeds a previously
stored predetermined deceleration to increase speed reduction,
hold a threshold value defined according to the deceleration if it
has been decided that the detected deceleration of the vehicle
exceeds the previously stored predetermined deceleration to
increase the speed reduction, and then decide whether or not the
speed integral value exceeds the predetermined threshold value
being held for this time duration,
output a start signal for the second inflator if it has been
decided that the speed integral value exceeds the predetermined
threshold value being held;
a memory device operable to store the program, which is executed by
said central processing unit, to be readable by said central
processing unit;
a D/A converter operable to convert a digital start signal, which
is supplied from said central processing unit to the first inflator
and the second inflator, into an analog signal; and
an interface circuit operable to convert an output signal of said
D/A converter into predetermined signals which are suitable for the
first inflator and the second inflator, respectively.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to start control of a passenger
protection system and, more particularly, to an improvement in
start control of a two-stage passenger protection system which has
two inflators and is constructed to fire them in order under
predetermined conditions.
2. Description of the Related Art
In the prior art, in the passenger protection system which is
represented by the air bag system, for example, such an air bag
system that inflates an air bag at a time when a impact
acceleration in excess of a predetermined reference is detected has
been the mainstream. However, according to various later studies,
experiments, etc., it becomes apparent that in some cases it is not
always proper for the passenger protection to inflate the air bag
at a stretch.
In recent years, various two-stage air bag systems have been
proposed from a viewpoint of passenger protection (for example, see
Patent Application Publication (KOKAI) Hei 2-310143, etc.). In such
two-stage air bag systems, a first stage inflator is fired under
predetermined conditions to inflate the air bag until a
predetermined size, and then a second stage inflator is fired to
inflate the air bag up to its maximum at a point of time when
second predetermined conditions are satisfied.
In such two-stage air bag systems, it becomes an issue from a
viewpoint of proper passenger protection how the first stage
inflator and the second stage inflator should be fired.
As a relatively simple method of firing the inflators, for example,
the start control can be thought of such that a deceleration caused
in a crash is measured so as to calculate its integral value and
then the first stage inflator and the second stage inflator are
fired respectively when such integral value exceeds respective
threshold values.
Such start control can be employed enoughly enoughly in practical
use unless so-called stagnation of the integral value of the
deceleration is caused between the fire of the first stage inflator
and fire of the second stage inflator.
However, according to the type of the crash, sometimes such a
phenomenon is produced that, since increase in the integral value
of the deceleration becomes small, i.e., a stagnation state is
generated after the first stage inflator has been fired, the
integral value of the deceleration hardly exceeds the threshold
value to generate firing of the second stage inflator, although
fire of the second stage inflator is requested. For example, in the
case of the so-called offset crash, because a part of constituent
parts of the vehicle is damaged by the impact, sometimes the
integral value of the deceleration is stagnated after the first
stage inflator has been fired. In the above type of crash, the case
is sometimes caused where, only if fire of the inflators is
determined based on the decision whether or not the integral value
of the deceleration exceeds the threshold value being set under
aforementioned simple conditions, the second stage inflator cannot
be fired in a period of time when fire of the second stage inflator
is truly needed.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a start
controlling method for a passenger protection system and a start
controlling system for a passenger protection system both capable
of executing start control of the passenger protection system which
has two-stage inflator appropriately, and a recording medium for
recording a start controlling program for the passenger protection
system.
It is another object of the present invention to provide a start
controlling method for a passenger protection system and a start
controlling system for a passenger protection system both capable
of firing a second inflator without fail if a crash needing to
start fire of the second inflator occurs after a first inflator has
been fired even under the situation that so-called stagnation of a
time integral value of deceleration is caused, and a recording
medium for recording a start controlling program for the passenger
protection system.
In order to achieve the object of the present invention, according
to a first aspect of the present invention, there is provided a
start controlling method for a passenger protection system, for
controlling start of the passenger protection system which has a
first inflator and a second inflator and is constructed such that a
protection system for protecting passengers of a vehicle is started
by firing the first inflator and the second inflator respectively
in response to a start signal from an external device, the method
comprising the steps of:
detecting a deceleration of a vehicle;
calculating a speed integral value which is time integration of the
deceleration;
deciding whether or not the speed integral value exceeds a first
predetermined threshold value, and then starting the first inflator
if it has been decided that the speed integral value exceeds the
first predetermined threshold value;
comparing a detected deceleration of the vehicle with a previously
stored predetermined deceleration for a first predetermined time
after the first inflator has been started, then deciding whether or
not the detected deceleration of the vehicle exceeds the previously
stored predetermined deceleration to increase speed reduction, and
then executing time integration over an area, in which the detected
deceleration of the vehicle exceeds the previously stored
predetermined deceleration, for a second predetermined time if it
has been decided that the detected deceleration of the vehicle
exceeds the previously stored predetermined deceleration to
increase the speed reduction;
adding the time integral value to a speed integral value which is
calculated as time integration of the detected deceleration of the
vehicle until a point of time when it has been decided that the
detected deceleration of the vehicle exceeds the previously stored
predetermined deceleration to increase the speed reduction; and
deciding whether or not an added result exceeds a second
predetermined threshold value, and then executing start of the
second inflator if it has been decided that the added result
exceeds the second predetermined threshold value.
Such start controlling method has been made in view of the fact
that, if increase of the speed integral value becomes slow, i.e.,
stagnation of the speed integral value is caused, after the first
inflator has been fired but the deceleration in excess of a
predetermined value is caused, fire of the second inflator must be
needed.
More particularly, in various types of crashes which needs firing
of the first inflator but does not need fire of the second
inflator, data of change in the deceleration caused when the
deceleration is increased up to its maximum (in other words, the
acceleration is increased to the negative side) are collected
previously according to the experiment, etc., and stored, and then
the detected deceleration of the vehicle is compared with the
stored deceleration after the first inflator has been fired. Then,
if the detected deceleration of the vehicle exceeds the stored
deceleration so as to increase speed reduction, time integration is
carried out over an area, in which the detected deceleration of the
vehicle exceeds the stored deceleration so as to increase speed
reduction, until the desired fire time of the second inflator.
Then, the integrated value is added to the speed integral value
calculated at a point of time when it has been decided that the
detected deceleration of the vehicle exceeds the stored
deceleration so as to increase speed reduction. Then, when the
added result exceeds a predetermined threshold value, start of the
second inflator is executed. As a result, even if the stagnation of
the speed integral value is caused, the second inflator can be
fired without fail.
In order to achieve the object of the present invention, according
to a second aspect of the present invention, there is provided a
start controlling system for a passenger protection system, for
controlling start of the passenger protection system which has a
first inflator and a second inflator and is constructed such that a
protection system for protecting passengers of a vehicle is started
by firing the first inflator and the second inflator respectively
in response to a start signal from an external device, the system
comprising:
a first integrating means for executing time integration with
respect to a deceleration of a vehicle input from an external
device;
a first integral value deciding means for deciding whether or not a
value calculated by the first integrating means exceeds a first
predetermined threshold value;
an acceleration deciding means for deciding whether or not the
deceleration of the vehicle input from the external device exceeds
a previously stored predetermined deceleration after a point of
time when it is decided by the first integral value deciding means
that the value calculated by the first integrating means exceeds
the first predetermined threshold value;
a second integrating means for executing time integration over an
area, in which the deceleration of the vehicle input from the
external device exceeds the previously stored predetermined
deceleration, for a predetermined time after a point of time when
it has been decided that the deceleration of the vehicle input from
the external device exceeds the previously stored predetermined
deceleration;
an adding means for adding an integral value, which is calculated
by the first integrating means when it is decided by the
acceleration deciding means that the deceleration of the vehicle
input from the external device exceeds the previously stored
predetermined deceleration, to an integral value calculated by the
second integrating means;
a second integral value deciding means for deciding whether or not
a value calculated by the adding means exceeds a second
predetermined threshold value; and
a start signal outputting means for outputting a start signal for
the first inflator when it has been decided by the first integral
value deciding means that the value calculated by the first
integrating means exceeds the first predetermined threshold value,
and outputting a start signal for the second inflator when it has
been decided by the second integral value deciding means that the
value calculated by the adding means exceeds the second
predetermined threshold value.
The start controlling system for the passenger protection system
having such configuration enables the start controlling method for
the passenger protection system to control start of the passenger
protection system. Respective means can be implemented by executing
the predetermined program by the CPU, for example.
In order to achieve the object of the present invention, according
to a third aspect of the present invention, there is provided a
start controlling system for a passenger protection system, for
controlling start of the passenger protection system which has a
first inflator and a second inflator and is constructed such that a
protection system for protecting passengers of a vehicle is started
by firing the first inflator and the second inflator respectively
in response to a start signal from an external device, the system
comprising:
a central processing unit, based on a predetermined program loaded
from an external device,
for executing time integration with respect to an externally input
deceleration of a vehicle,
deciding whether or not a time integral value exceeds a first
predetermined threshold value, and then outputting a start signal
for the first inflator if it has been decided that the time
integral value exceeds the first predetermined threshold value,
comparing a detected deceleration of the vehicle with a previously
stored predetermined deceleration for a first predetermined time
after the first inflator has been started, then deciding whether or
not the detected deceleration of the vehicle exceeds the previously
stored predetermined deceleration to increase speed reduction, and
then executing time integration over an area, in which the detected
deceleration of the vehicle exceeds the previously stored
predetermined deceleration, for a second predetermined time
thereafter if it has been decided that the detected deceleration of
the vehicle exceeds the previously stored predetermined
deceleration to increase the speed reduction,
adding the time integral value to a speed integral value which is
calculated as time integration of the detected deceleration of the
vehicle until a point of time when it has been decided that the
detected deceleration of the vehicle exceeds the previously stored
predetermined deceleration to increase the speed reduction, and
deciding whether or not an added result exceeds a second
predetermined threshold value, and then outputting a start signal
for the second inflator if it has been decided that the added
result exceeds the second predetermined threshold value;
a memory device for storing the program, which is executed by the
central processing unit, to be readable by the central processing
unit;
a D/A converter for converting a digital start signal, which is
supplied from the central processing unit to the first inflator and
the second inflator, into an analog signal; and
an interface circuit for converting an output signal of the D/A
converter into predetermined signals which are suitable for the
first inflator, and the second inflator respectively.
In order to achieve the object of the present invention, according
to a fourth aspect of the present invention, there is provided a
start controlling method for a passenger protection system, for
controlling start of the passenger protection system which has a
first inflator and a second inflator and is constructed such that a
protection system for protecting passengers of a vehicle is started
by firing the first inflator and the second inflator respectively
in response to a start signal from an external device, the method
comprising the steps of:
detecting a deceleration of a vehicle;
calculating a speed integral value which is time integration of the
deceleration;
deciding whether or not the speed integral value exceeds a
predetermined threshold value defined according to a detected
deceleration of the vehicle;
starting the first inflator if it has been decided that the speed
integral value exceeds the predetermined threshold value defined
according to the detected deceleration of the vehicle;
comparing the detected deceleration of the vehicle with a
previously stored predetermined deceleration for a predetermined
time after the first inflator has been started, then deciding
whether or not the detected deceleration of the vehicle exceeds the
previously stored predetermined deceleration to increase speed
reduction;
holding a threshold value defined according to the deceleration
until termination of the predetermined time thereafter if it has
been decided that the detected deceleration of the vehicle exceeds
the previously stored predetermined deceleration to increase the
speed reduction, and then deciding whether or not the speed
integral value exceeds the predetermined threshold value being held
for that time duration; and
starting the second inflator if it has been decided that the speed
integral value exceeds the predetermined threshold value being
held.
Such start controlling method has been made in view of the fact
that, if increase of the speed integral value becomes slow, i.e.,
stagnation of the speed integral value is caused, after the first
inflator has been fired but the deceleration in excess of a
predetermined value is caused, fire of the second inflator must be
needed.
More particularly, in various types of crashes which needs firing
of the first inflator but do not need firing of the second
inflator, data of change in the deceleration caused when the
deceleration is increased up to its maximum (in other words, the
acceleration is increased to the negative side) are collected
previously according to the experiment, etc., and stored, and then
the detected deceleration of the vehicle is compared with the
stored deceleration after the first inflator has been fired. Then,
if the detected deceleration of the vehicle exceeds the stored
deceleration to increase speed reduction, the threshold value
defined according to the deceleration of the vehicle at that time
is held for a predetermined time thereafter. Since the deceleration
of the vehicle which exceeds this threshold value being held can be
detected if the crash needs firing of the second inflator, start of
the second inflator is executed when it is decided that the
deceleration of the vehicle exceeds the threshold value. As a
result, even if the stagnation of the speed integral value is
caused, the second inflator can be fired without fail.
In order to achieve the object of the present invention, according
to a fifth aspect of the present invention, there is provided a
start controlling system for a passenger protection system, for
controlling start of the passenger protection system which has a
first inflator and a second inflator and is constructed such that a
protection system for protecting passengers of a vehicle is started
by firing the first inflator and the second inflator respectively
in response to a start signal from an external device, the system
comprising:
an integrating means for executing time integration with respect to
a deceleration of a vehicle input from an external device;
a first integral value deciding means for deciding whether or not a
value calculated by the integrating means exceeds a predetermined
threshold value defined according to the deceleration of the
vehicle;
an acceleration deciding means for deciding whether or not the
deceleration of the vehicle input from the external device exceeds
a previously stored predetermined deceleration to increase speed
reduction, for a predetermined time after a point of time when it
is decided by the first integral value deciding means that the
value calculated by the integrating means exceeds the predetermined
threshold value defined according to the deceleration of the
vehicle;
a second integrating means for holding a threshold value defined
according to the deceleration of the vehicle until termination of
the predetermined time when it has been decided by the acceleration
deciding means that the deceleration of the vehicle input from the
external device exceeds the previously stored predetermined
deceleration to increase the speed reduction, and then deciding
whether or not a value calculated by the integrating means exceeds
the predetermined threshold value being held for this time
duration; and
a start signal outputting means for outputting a start signal for
the first inflator when it has been decided by the first integral
value deciding means that the value calculated by the first
integrating means exceeds the first predetermined threshold value,
and outputting a start signal for the second inflator when it has
been decided by the second integral value deciding means that the
value calculated by the integrating means exceeds the predetermined
threshold value being held.
The start controlling system for the passenger protection system
having such configuration enables the start controlling method for
the passenger protection system to control start of the passenger
protection system. Respective means can be implemented by executing
the predetermined program by the CPU, for example.
In order to achieve the object of the present invention, according
to a sixth aspect of the present invention, there is provided a
start controlling system for a passenger protection system, for
controlling start of the passenger protection system which has a
first inflator and a second inflator and is constructed such that a
protection system for protecting passengers of a vehicle is started
by firing the first inflator and the second inflator respectively
in response to a start signal from an external device, the system
comprising:
a central processing unit, based on a predetermined program loaded
from an external device,
for executing time integration with respect to an externally input
deceleration of a vehicle,
deciding whether or not a time integral value exceeds a
predetermined threshold value defined according to the externally
input deceleration of the vehicle,
outputting a start signal for the first inflator if it has been
decided that the time integral value exceeds a predetermined
threshold value defined according to a detected deceleration of the
vehicle,
comparing the detected deceleration of the vehicle with a
previously stored predetermined deceleration for a predetermined
time after the first inflator has been started, then deciding
whether or not the detected deceleration of the vehicle exceeds a
previously stored predetermined deceleration to increase speed
reduction,
holding a threshold value defined according to the deceleration if
it has been decided that the detected deceleration of the vehicle
exceeds the previously stored predetermined deceleration to
increase the speed reduction, and then deciding whether or not the
speed integral value exceeds the predetermined threshold value
being held for this time duration,
outputing a start signal for the second inflator if it has been
decided that the speed integral value exceeds the predetermined
threshold value being held;
a memory device for storing the program, which is executed by the
central processing unit, to be readable by the central processing
unit;
a D/A converter for converting a digital start signal, which is
supplied from the central processing unit to the first inflator and
the second inflator, into an analog signal; and
an interface circuit for converting an output signal of the D/A
converter into predetermined signals which are suitable for the
first inflator and the second inflator respectively.
In order to achieve the object of the present invention, according
to a seventh aspect of the present invention, there is provided a
recording medium for recording a plurality of computer-readable
instructions, comprising:
a first instruction means for causing a computer to execute time
integration with respect to a deceleration of a vehicle input from
an external device;
a second instruction means for causing the computer to decide
whether or not a time integral value exceeds a first predetermined
threshold value;
a third instruction means for causing the computer to output a
start signal for the first inflator if it is decided that the time
integral value exceeds the first predetermined threshold value;
a fourth instruction means for causing the computer to decide
whether or not the deceleration of the vehicle exceeds a previously
stored predetermined deceleration, for a first predetermined time
after the start signal has been output to the first inflator;
a fifth instruction means for causing the computer to execute time
integration over an area, in which the deceleration of the vehicle
exceeds the previously stored predetermined deceleration, for a
second predetermined time thereafter if it is decided that the
deceleration of the vehicle exceeds the previously stored
predetermined deceleration;
a sixth instruction means for causing the computer to execute an
addition calculation of the calculated time integral value and the
time integral value of the deceleration of the vehicle, which is
calculated until a point of time when it is decided that the
deceleration of the vehicle exceeds the previously stored
predetermined deceleration;
a seventh instruction means for causing the computer to decide
whether or not a result of the addition calculation exceeds a
second predetermined threshold value; and
an eighth instruction means for causing the computer to output a
start signal for the second inflator if it is decided that the
result of the addition calculation exceeds the second predetermined
threshold value.
Such recording medium is fit to cause the computer to execute the
method according to the invention.
In order to achieve the object of the present invention, according
to an eighth aspect of the present invention, there is provided a
recording medium for recording a plurality of computer-readable
instructions, comprising:
a first instruction means for causing a computer to execute
calculation of a time integration value with respect to a
deceleration of a vehicle input from an external device;
a second instruction means for causing the computer to decide
whether or not the time integral value exceeds a predetermined
threshold value defined according to a detected deceleration of the
vehicle;
a third instruction means for causing the computer to output a
start signal for the first inflator if it is decided that the time
integral value exceeds the predetermined threshold value;
a fourth instruction means for causing the computer to decide
whether or not a detected deceleration of the vehicle exceeds a
previously stored predetermined deceleration to increase speed
reduction, for a predetermined time after the first inflator has
been started;
a fifth instruction means for causing the computer to hold a
threshold value defined according to the deceleration of the
vehicle until termination of the predetermined time if it is
decided that the detected deceleration of the vehicle exceeds the
previously stored predetermined deceleration to increase the speed
reduction, and then causing the computer to decide whether or not
the time integral value of the deceleration of the vehicle exceeds
the predetermined threshold value being held; and
a sixth instruction means for causing the computer to output a
start signal for the second inflator if it is decided that the time
integral value of the deceleration of the vehicle exceeds the
predetermined threshold value being held.
Such recording medium is fit to cause the computer to execute the
method according to the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view showing an example of a configuration of
a start controlling system for a passenger protection system
according to embodiments of the present invention;
FIG. 2 is a flowchart showing procedures of start control of the
passenger protection system according to a first embodiment of the
present invention;
FIG. 3 is a flowchart showing procedures of start control of the
passenger protection system according to a second embodiment of the
present invention;
FIG. 4 is a characteristic diagram showing an example of change in
characteristic curves of stored deceleration G.sub.M and
deceleration G which needs fire of a second inflator even when
stagnation of a speed integral value is caused after a first
inflator has been fired, in the first embodiment of the present
invention;
FIG. 5 is a characteristic diagram showing change in characteristic
curves of the speed integral value relative to the deceleration
G.sub.M and the deceleration G shown in FIG. 4;
FIG. 6 is a characteristic diagram showing an example of change in
characteristic curves of stored deceleration G.sub.M and
deceleration G which needs fire of a second inflator even when
stagnation of a speed integral value is caused after a first
inflator has been fired, in the second embodiment of the present
invention;
FIG. 7 is a characteristic diagram showing change in characteristic
curves of the speed integral value relative to the deceleration
G.sub.M and the deceleration G shown in FIG. 6; and
FIG. 8 is a view showing an example of a configuration in which a
floppy disk is employed to read the program.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention will be explained in detail
with reference to the accompanying drawings hereinafter.
Members, arrangements, etc., described hereinafter should not be
interpreted not to limit the present invention and they may be
variously modified and changed within the scope and spirit of the
present invention.
First, a basic configuration of a start controlling system for a
passenger protection system according to embodiments of the present
invention (referred to as "present system" hereinafter) will be
explained with reference to FIG. 1.
As shown in FIG. 1, a so-called hardware configuration of the
present system S comprises a first interface circuit (labeled as
"I/F (1)" in FIG. 1) 1, an analog/digital converter (labeled as
"A/D" in FIG. 1) 2, a ROM (Read Only Memory) 3, a central
processing unit (labeled as "CPU" in FIG. 1) 4, a RAM (Random
Access Memory) 5, a digital/analog converter (labeled as "D/A" in
FIG. 1) 6, and a second interface circuit (labeled as "I/F (2)" in
FIG. 1) 7.
The first interface circuit 1 converts a level of an analog output
signal from an acceleration sensor 8 which detects an acceleration
of a vehicle. The analog output signal is converted into a digital
signal by the analog/digital converter 2, which has a well known
circuit configuration, and then input into the central processing
unit 4.
In this case, as the so-called acceleration sensor which is well
known, there are semiconductor type sensors, piezo-electric type
sensors, etc. But the acceleration sensor 8 in the present system S
must not be limited to a particular type sensor, and therefore any
type sensor may be employed.
The ROM 3 readably stores a program for implementing start
controlling operations described later, various data such as
constants, etc. The ROM 3 consists of a memory which is formed as a
well known integrated circuit.
The central processing unit 4 executes start control described
later when the program for start control of the passenger
protection system is loaded into the CPU 4. For example, the CPU 4
consists of a well known CPU being formed as a so-called IC, and
carries out start control described later when the program for
start control of the passenger protection system is loaded
thereinto. In place of this CPU 4, other integrated circuits, e.g.
a DSP (Digital Signal Processor), which is known as an integrated
circuit to enable the high speed arithmetic process, etc., may be
employed if they can achieve equivalent functions to those of the
CPU 4.
The RAM 5 is a memory device which is formed as well known the
integrated circuit like the ROM 3. The results of arithmetic
operations executed by the CPU 4, etc., can be stored/read
into/from the RAM 5.
The digital/analog converter 6 converts a digital start signal,
which is output from the CPU 4 to a first inflator 9A and a second
inflator 9B, into an analog start signal. The digital/analog
converter 6 has a well known circuit configuration.
The second interface circuit 7 converts control signals being
output from the CPU 4 via the digital/analog converter 6, i.e. a
start signal for starting the first inflator 9A and a start signal
for starting the second inflator 9B, into a signal level and a
signal format which are fit to be input into the first inflator 9A
and the second inflator 9B respectively, and then outputs converted
control signals.
The air bag system 9 comprises the first inflator (gas generator)
9A and the second inflator (gas generator) 9B. As described later,
in this two-stage air bag system 9, at first the first stage
inflator 9A is started under predetermined conditions to thus
generate a gas until an air bag main body (not shown) is inflated
up to an appropriate size, and then the second stage inflator 9B is
started to generate the gas similarly until the air bag main body
is inflated up to its maximum size.
Next, prior to the explanation of procedures of particular start
control effected by the CPU 4, a basic concept of start control in
the first embodiment of the present invention will be explained
with reference to FIGS. 4 and 5.
Start control in the first embodiment intends to prevent such a
situation that increase in the speed integral value .DELTA.V which
is the integral value of the so-called deceleration becomes small
(in other words, an absolute value of a change rate of the speed
integral value .DELTA.V is reduced), i.e., a so-called stagnation
state is generated after the first stage inflator 9A has been
started, and therefore the second stage inflator 9B cannot be
appropriately started since it is not decided that start of the
second stage inflator 9B is requested because of such stagnation of
the speed integral value .DELTA.V although essentially start of the
second stage inflator 9B is requested.
More particularly, according to the type of the crash, sometimes
there are cases where fire of the first stage inflator 9A is
requested but fire of the second stage inflator 9B is not
requested. In start control in the first embodiment, in various
changes in characteristic curves of various decelerations G caused
in such cases where fire of the first stage inflator 9A is
requested but fire of the second stage inflator 9B is not
requested, at first data are collected in the case where the change
in the deceleration G is maximized to the negative side, and then a
value of the deceleration G is stored as G.sub.M over a
predetermined period of time.
It is preferable that this data collection should be effected based
on the experiment, simulation by the computer, etc. Also, it is
preferable that data of G.sub.M should be stored in the ROM 3, for
example.
In FIG. 4, an example of a characteristic curve is indicated by a
solid line when the change in the deceleration G is maximized to
the negative side, in various changes in characteristic curves of
various decelerations G caused in such cases where fire of the
first stage inflator 9A is requested but fire of the second stage
inflator 9B is not requested.
More particularly, in the case of this characteristic curve, the
deceleration G is increased relatively smoothly (in other words,
increased to the negative side) with the lapse of time until it is
passed through a first stage fire time T1 of the first stage
inflator 9A. Then, the deceleration G is reduced rapidly (in other
words, directed toward the positive side) from a point of time
slightly before the intermediate point between the first stage fire
time T1 of the first stage inflator 9A and a second stage fire time
T2 of the second stage inflator 9B. Then, after the deceleration G
has been reduced to some extent, it is increased rapidly for the
second time. Then, such second rapid increase of the deceleration G
becomes gentle from a point of time a little before the second
stage fire time T2 of the second stage inflator 9B (see the
characteristic curve indicated by the solid line in FIG. 4).
In FIG. 5, the speed integral value .DELTA.V which is the time
integration of the deceleration G is given by the characteristic
curve being indicated by the broken line.
More particularly, in this case, the speed integral value .DELTA.V
exceeds a predetermined threshold value V.sub.TH1 before the first
stage fire time T1 of the first stage inflator 9A, and is increased
up to the second stage fire time T2 of the second stage inflator 9B
with change in the deceleration G. Then, increase in the speed
integral value .DELTA.V, i.e. an absolute value of the change rate,
is reduced gradually near the second stage fire time T2, and then
the speed integral value .DELTA.V exceeds a predetermined threshold
value V.sub.TH2 at last when it passes through the second stage
fire time T2. It is decided that fire of the second stage inflator
9B is needed when the speed integral value .DELTA.V exceeds the
predetermined threshold value V.sub.TH2 (see the characteristic
curve indicated by the broken line in FIG. 5).
Out of the above changes in the deceleration collected by the
experiment, etc., data collected between the first stage fire time
T1 of the first stage inflator 9A and the desired second stage fire
time T2 of the second stage inflator 9B are stored in the ROM 3
(see FIG. 4).
According to this start control, after the first stage inflator 9A
has been fired, the detected deceleration G and the stored
deceleration G.sub.M are compared with each other at an appropriate
time interval, and then time interval of difference between the
deceleration G and the deceleration G.sub.M is calculated from a
point of time when the detected deceleration G is increased larger
than the stored deceleration G.sub.M (the deceleration G exceeds
the deceleration G.sub.M toward the negative side) to the desired
second stage fire time T2 of the second stage inflator 9B. Then,
the time integral value is added to the speed integral value
.DELTA.V which is the time integral value of the deceleration G
calculated until the previous first stage fire time T1 of the first
stage inflator 9A. If such added value exceeds the predetermined
threshold value V.sub.TH2, the second stage inflator 9B is
started.
For instance, an example of change in characteristic curves of the
deceleration G in the case where fire of both the first stage
inflator 9A and the second stage inflator 9B is requested is
indicated by a chain double-dashed line in FIG. 4.
In the case of this example of change in characteristic curves of
the deceleration G being indicated by the chain double-dashed line,
the deceleration G is increased at first to some extent (increased
to the negative side), then is immediately turn to decrease, and
then starts to increase again. Then, the deceleration G comes up to
a peak on the negative side at a point of time near the first stage
fire time T1 of the first stage inflator 9A, and then is reduced
once again until a point of time before the almost middle between
the first stage fire time T1 of the first stage inflator 9A and the
desired second stage fire time T2 of the second stage inflator 9B
(see FIG. 4). Where "the desired second stage fire time T2" means a
point of time which can be expanded at its maximum as the fire time
of the second stage inflator 9B with respect to the proper
passenger protection after the first stage inflator 9A has been
fired. The desired second stage fire time T2 has a meaning that, if
the second stage inflator 9B is fired after this second stage fire
time T2, there is a possibility that proper protection of the
passenger cannot be achieved.
Then, the deceleration G is increased abruptly once again, then
comes up to a peak on the negative side around the almost middle
between the first stage fire time T1 of the first stage inflator 9A
and the desired second stage fire time T2 of the second stage
inflator 9B, then is directed to decrease three times, and then is
increased rapidly three times when it is decreased to some extent
(see FIG. 4). This increase in the deceleration G for the third
time becomes gentle from a point of time before the desired second
stage fire time T2 of the second stage inflator 9B.
Such speed integral value .DELTA.V of the deceleration G, if
calculated, may be indicated by the characteristic curve indicated
by the solid line in FIG. 5.
More particularly, the speed integral value .DELTA.V is increased
(i.e., increased to the negative side) with the increase in the
deceleration G until reduction in the deceleration G is generated
for the first time, and then so-called stagnation of integration is
caused (see near a reference a in FIG. 5) after the first reduction
in the deceleration G has been caused. Then, such stagnation state
can be solved to thus increase the speed integral value .DELTA.V
with the increase in the deceleration G, and then exceed the
predetermined threshold value V.sub.TH1.
However, with the second reduction in the deceleration G after
this, stagnation of the integral value is caused once again before
the desired second stage fire time T2 of the second stage inflator
9B (see a location indicated by a reference b in FIG. 5).
Therefore, the speed integral value .DELTA.V has not yet exceeded
the predetermined threshold value V.sub.TH2, which indicates the
need of fire of the second stage inflator 9B, at the desired second
stage fire time T2, but the speed integral value .DELTA.V exceeds
the predetermined threshold value V.sub.TH2 after it has passed
through the desired second stage fire time T2 (see the
characteristic curve indicated by the solid line in FIG. 5).
Therefore, in this start control, after the first stage inflator 9A
has been fired, the time integration as to a portion where the
deceleration G exceeds the deceleration G.sub.M, i.e. the integral
value corresponding to an area of the hatched portion (such
integral value is referred to as a "temporary integral value
.DELTA.Vtemp" hereinafter) in the example in FIG. 4, is added to
the speed integral value .DELTA.V which is derived until the
deceleration G exceeds the deceleration G.sub.M (see a point of
time T3 in FIG. 4), and then the result is set as the speed
integral value .DELTA.V. According to such process, as shown by the
characteristic curve being indicated by the chain double-dashed
line, the speed integral value .DELTA.V can exceed sufficiently the
predetermined threshold value V.sub.TH2 at the desired second stage
fire time T2 of the second stage inflator 9B without stagnation
after the deceleration G has exceeded the deceleration G.sub.M, so
that the second stage inflator 9B can be fired without fail.
Next, detailed procedures of start control of the passenger
protection system according to the first embodiment of the present
invention will be explained with reference to a flowchart shown in
FIG. 2 hereunder.
If an operation of the CPU 4 is commenced, initialization of
various variables, etc., is first executed (see step 100 in FIG.
2). Then, the deceleration G detected by an acceleration sensor 8
is input into the CPU 4 via the first interface circuit 1 and the
analog/digital converter 2 (see step 102 in FIG. 2).
Time integration of the deceleration G loaded into the CPU 4 is
then executed to calculate the speed integral value .DELTA.V (see
step 104 in FIG. 2).
The process then advances to step 106 wherein it is decided whether
or not a state decision flag F1 is set to "1" (see step 106 in FIG.
2).
As described later, the state decision flag F1 is set to "1"
immediately after the first stage inflator 9A has been started, and
conversely is set to "0" when it has been decided that start of the
second stage inflator 9B is not needed. The state "1" means that
the state decision flag F1 is in a state to decide whether or not
start of the second stage inflator 9B is requested.
In step 106, if it has been decided that F1=1 (if YES), the process
goes to step 116 described later. In contrast, in step 106, if it
has been decided that F1.noteq.1 (if NO), then it is decided
whether or not the speed integral value .DELTA.V exceeds the
predetermined threshold value V.sub.TH1 to take a value on the more
negative side (see step 108 in FIG. 2).
Then, if it has been decided that the speed integral value .DELTA.V
does not exceed the predetermined threshold value V.sub.TH1 to take
the value on the more negative side (i.e., .DELTA.V<V.sub.TH1
has not been satisfied yet) (if NO), it is decided that the speed
integral value .DELTA.V is not in such a state that is decided as
generation of the clash, and then the process returns to previous
step 102. Then, a series of processes are repeated once again.
Here the predetermined threshold value V.sub.TH1 shows the
magnitude of the speed integral value when it is decided that the
first stage inflator 9A is started (see FIG. 5). This threshold
value V.sub.TH1 is calculated by using a preset relation based on
the magnitude of the deceleration G at this point of time,
otherwise is calculated by using a previously stored conversion
table which stipulates a relation between the deceleration G and
the threshold value V.sub.TH1. Then, the calculated threshold value
V.sub.TH1 is set. This method of setting the threshold value
V.sub.TH1 is similar to the prior art.
A particular relation between the deceleration G and the threshold
value V.sub.TH1 is omitted herein. Roughly speaking, a level of the
deceleration G at which the first stage inflator 9A is to be fired
in the frontal crash, for example, is calculated from simulation
data derived by the experiment or the computer, and then this
relation is set based on the level of the deceleration G. With
regard to the fact that the deceleration G is caused differently
according to the vehicle type, an appropriate relation between the
deceleration G and the threshold value V.sub.TH1 can be set every
vehicle type.
On the contrary, if it has been decided that .DELTA.V<V.sub.TH1
is satisfied (if YES), i.e., it has been decided that the first
stage inflator 9A must be fired, the start signal is then output
from the CPU 4 to the first stage inflator 9A via the D/A converter
6 and the second interface circuit 7. Then, the first stage
inflator 9A is fired (see step 110 in FIG. 2).
Next, when the first stage inflator 9A is fired, the state decision
flag F1 is set to "1" (see step 112 in FIG. 2). Then, a timer is
started and then the process returns to previous step 102 (see step
114 in FIG. 2). This timer is used for time count, and is
constructed to count a lapse time from start of the timer according
to the well known software.
In contrast, it has been decided that F1=1 in step 106, the process
proceeds to step 116. In step 116, it is decided whether or not the
deceleration G which has been loaded into the CPU 4 by the process
in previous step 102 exceeds the deceleration G.sub.M being stored
previously in the ROM 3 (see step 116 in FIG. 2).
In this case, as has been explained previously with reference to
FIGS. 4 and 5, the deceleration G.sub.M denotes data of the
deceleration which are collected based on the experiment, the
simulation by using the computer, etc., and ranges between the
first stage fire time T1 of the first stage inflator 9A and the
desired second stage fire time T2 of the second stage inflator 9B.
Where the desired second stage fire time T2 of the second stage
inflator 9B is set at a point of time after the first stage fire
time T1 of the first stage inflator 9A by about 20 msec, for
example.
If the decelerations G.sub.M are stored into the ROM 3, they give
discrete data of the deceleration which are taken at a
predetermined time interval for a lapse time from the first stage
fire time T1 of the first stage inflator 9A as a starting
point.
Accordingly, it is preferable that the time interval at which the
decelerations G are loaded by the acceleration sensor 8 should be
set to be identical to the time interval of the data of the
decelerations G.sub.M stored into the ROM 3. If respective time
intervals are different, the decelerations G.sub.M may be decided
at concerned points of time by the well known interpolation
process.
In step 116, if it has been decided that
.vertline.G.vertline.<.vertline.G.sub.M.vertline. (stored data
G.sub.M is increased to the negative side much more than the
deceleration G being detected by the acceleration sensor 8), it is
decided that the crash is not in the condition wherein fire of the
second stage inflator 9B is requested. Then, the process goes to
step 128. Instep 128, it is decided whether or not the lapse time
from the first stage fire time T1 of the first stage inflator 9A
exceeds a predetermined period of time Ta.
If it has been decided that the lapse time T exceeds the
predetermined period of time Ta (if YES), it is decided that the
crash has not come up to the extent that fire of the second stage
inflator 9B must be requested, and then the process is ended (see
step 128 in FIG. 2). Conversely, if it has been decided that the
lapse time T does not exceed the predetermined period of time Ta
(if NO), the process advances to step 124 (see step 128 in FIG.
2).
In this case, the predetermined period of time Ta is a time
interval between the first stage fire time T1 of the first stage
inflator 9A and the desired second stage fire time T2 of the second
stage inflator 9B.
On the contrary, in previous step 116, if it has been decided that
.vertline.G.vertline.>.vertline.G.sub.M.vertline. (the
deceleration G being detected by the acceleration sensor 8 exceeds
stored data G.sub.M much more to the negative side) (in other
words, the deceleration of the vehicle exceeds a predetermined
deceleration to thus increase the speed reduction much more), time
integration of difference between the deceleration G and the
deceleration G.sub.M is executed to calculate the temporary (time)
integral value .DELTA.Vtemp (see step 118 in FIG. 2). That is to
say, as has been explained with reference to FIGS. 4 and 5
previously, assume that the stored data G.sub.M is given by the
characteristic curve indicated by the solid line in FIG. 4 and the
deceleration G detected by the acceleration sensor 8 is given by
the characteristic curve indicated by the chain double-dashed line
in FIG. 4, calculation of the temporary integral value .DELTA.Vtemp
corresponds to calculation of an area of a portion surrounded by
above two characteristic curves (a hatched area in FIG. 4). In
other words, as for an area in which the detected deceleration G
exceeds the stored data G.sub.M to increase to the negative side,
time integration is executed.
After the above temporary integral value .DELTA.Vtemp has been
calculated, it is decided whether or not the lapse time T from the
first stage fire time T1 of the first stage inflator 9A exceeds the
predetermined period of time Ta (see step 120 in FIG. 2). If it has
been decided that the lapse time T exceeds the predetermined period
of time Ta (if YES), the process is then terminated.
In contrast, if it has been decided that the lapse time T does not
exceed the predetermined period of time Ta (if NO), the process is
conducted in which the speed integral value .DELTA.V (see step 104
in FIG. 2) calculated until it has been decided that
.vertline.G.vertline.>.vertline.G.sub.M.vertline. (see step 116
in FIG. 2) is added to the above temporary integral value
.DELTA.Vtemp. Then, the added result is set to the new speed
integral value .DELTA.V (see step 122 in FIG. 2).
Then, it is decided whether or not the speed integral value
.DELTA.V calculated in step 122 exceeds the predetermined threshold
value V.sub.TH2 to extend to the negative side
(.DELTA.V<V.sub.TH2) (see step 124 in FIG. 2). Where the
predetermined threshold value V.sub.TH2 is determined in compliance
with the experiment, the simulation by the computer, etc. More
particularly, according to the experiment, etc., the temporary
integral value .DELTA.Vtemp is calculated as above and also the
value added to the speed integral value .DELTA.V is calculated, and
then the predetermined threshold value V.sub.TH2 is selected among
such data and set as the value which is suitable for the decision
of fire of the second stage inflator 9B.
In step 124, if it has been decided that .DELTA.V<V.sub.TH2 is
satisfied (If YES), i.e. if It has been decided that the crash is
in the state where fire of the second stage inflator 9B is
requested, the start signal is output from the CPU 4 to the second
stage Inflator 9B via the D/A converter 6 and the second interface
circuit 7 and then the second stage Inflator 9B is fired (see step
126 in FIG. 2).
On the other hand, in step 124, if it has been decided that
.DELTA.V<V.sub.TH2 is not satisfied (if NO), i.e. if it has been
decided that there is no need to fire the second stage inflator 9B,
the process returns to step 102. Then, a series of processes are
repeated newly.
In the above first embodiment, a first integrating means can be
implemented by carrying out step 104 by the CPU 4, a first integral
value deciding means can be implemented by carrying out step 108 by
the CPU 4, an acceleration deciding means can be implemented by
carrying out step 116 by the CPU 4, a second integrating means can
be implemented by carrying out steps 114, 118, 120 by the CPU 4, an
adding means can be implemented by carrying out step 122 by the CPU
4, a second integral value deciding means can be implemented by
carrying out step 124 by the CPU 4, and a start signal outputting
means can be implemented by carrying out steps 110, 126 by the CPU
4.
Next, a second embodiment will be explained with reference to FIGS.
1 and 3 and FIGS. 6 and 7 hereunder.
A so-called hardware configuration of a start control system S of a
passenger protection system according to a second embodiment of the
present invention is identical to that shown previously in FIG. 1
previously and no particular difference resides between them.
Therefore, a detailed explanation thereof is omitted and FIG. 1
will be referred to in the following explanation as the need
arises.
To begin with, the second embodiment will be schematically
explained while comparing with the above first embodiment. First,
in the above first embodiment, the time integration of an area
where the deceleration G being detected by the acceleration sensor
8 exceeds the previously stored deceleration G.sub.M to increase to
the negative side (G<G.sub.M) is calculated, and then the time
integral value is added to the speed integral value .DELTA.V at a
point of time when G<G.sub.M is satisfied. Therefore, even if
stagnation of the deceleration G is caused after the first stage
inflator 9A has been fired, the deceleration G can exceed the
predetermined threshold value V.sub.TH2 to thus ensure the fire of
the second stage inflator 9B without fail.
In contrast, in the second embodiment, the threshold value
V.sub.TH2 is held at a point of time when G<G.sub.M is
satisfied, and then fire of the second stage inflator 9B is
executed when the speed integral value .DELTA.V exceeds this held
threshold value V.sub.TH2.
Then, detailed procedures of start control will be explained with
reference to a flowchart shown in FIG. 3 hereunder. In FIG. 3, the
same step numbers as those shown in FIG. 2 are affixed to steps for
executing the same processes as those in the flowchart shown in
FIG. 2.
When an operation of the CPU 4 is commenced, initialization of
various variables, etc., is first executed (see step 100 in FIG.
3). Then, the deceleration G detected by the acceleration sensor 8
is input into the CPU 4 via the first interface circuit 1 and the
analog/digital converter 2 (see step 102 in FIG. 3).
Time integration of the deceleration G being loaded into the CPU 4
is then executed to thus calculate the speed integral value
.DELTA.V (see step 104 in FIG. 3).
The process then advances to step 106, and then it is decided
whether or not the state decision flag F1 is set to "1" (see step
106 in FIG. 3).
As described later, the state decision flag F1 is set to "1"
immediately after the first stage inflator 9A has been started, and
conversely is set to "0" when it has been decided that start of the
second stage inflator 9B is not needed. The state "1" means that
the state decision flag F1 is in a state to decide whether or not
start of the second stage inflator 9B is requested.
In step 106, if it has been decided that F1=1 (if YES), then the
process goes to step 116 described later. In contrast, in step 106,
if it has been decided that F1.noteq.1 (if NO), then it is decided
whether or not the speed integral value .DELTA.V exceeds the
predetermined threshold value V.sub.TH1 to take a value on the more
negative side (see step 108 in FIG. 3).
Then, if it has been decided that the speed integral value .DELTA.V
does not exceed the predetermined threshold value V.sub.TH1 to take
the value on the more negative side (i.e., .DELTA.V<V.sub.TH1
has not been satisfied yet) (if NO), it is decided that the speed
integral value .DELTA.V is not in such a state that is decided as
generation of the crash, and then the process returns to previous
step 102. Then, a series of processes are repeated once again.
Here, as described previously in the explanation in step 108 in
FIG. 2, the threshold value V.sub.TH1 is set based on the magnitude
of the deceleration G by using a preset relation and a previously
stored conversion table.
On the contrary, if it has been decided that .DELTA.V<V.sub.TH1
is satisfied (if YES), i.e. it has been decided that the first
stage inflator 9A must be fired, the start signal is then output
from the CPU 4 to the first stage inflator 9A via the D/A converter
6 and the second interface circuit 7. Then, the first stage
inflator 9A is fired (see step 110 in FIG. 3).
Then, when the first stage inflator 9A is fired, the state decision
flag F1 is set to "1" (see step 112 in FIG. 3). Then, the timer is
started, and then the process returns to previous step 102 (see
step 114 in FIG. 3). This timer is used for time count, and is
constructed to count a lapse time from start of the timer according
to the well known software.
In contrast, in step 106, it has been decided that F1=1, the
process proceeds to step 116. In step 116, it is decided whether or
not the deceleration G which has been loaded into the CPU 4 by the
process in previous step 102 exceeds the deceleration G.sub.M being
stored previously in the ROM 3 (see step 116 in FIG. 3).
Here the deceleration G.sub.M will be explained with reference to
FIGS. 6 and 7. In this case, FIG. 6 is the same as above FIG. 4.
That is, in FIG. 6, the characteristic curve indicated by the solid
line corresponds to the case where the deceleration G is maximized
(becomes its maximum on the negative side) among changes in
characteristic curves of various decelerations G caused when fire
of the first stage inflator 9A is needed but fire of the second
stage inflator 9B is not needed. In addition, in FIG. 6, the
characteristic curve indicated by the chain double-dashed line
shows an example of change in characteristic curve of the
deceleration G at which both the first stage inflator 9A and the
second stage inflator 9B must be fired. In this example, stagnation
of the speed integral value .DELTA.V is caused after the first
stage inflator 9A has been fired.
FIG. 7 is basically identical to above FIG. 5 except that the
characteristic curve indicated by the chain double-dashed line in
FIG. 5 is not shown therein. That is, in FIG. 7, the characteristic
curve indicated by the broken line corresponds to change in the
characteristic curve of the speed integral value .DELTA.V with
respect to the deceleration G shown in the characteristic curve
indicated by the solid line in FIG. 6. Also, in FIG. 7, the
characteristic curve indicated by the solid line corresponds to
change in the characteristic curve of the speed integral value
.DELTA.V with respect to the deceleration G shown in the
characteristic curve indicated by the chain double-dashed line in
FIG. 6.
The deceleration G.sub.M stored in the ROM 3 is the same as
explained in the first embodiment. In other words, the deceleration
G.sub.M is the value of the characteristic curve indicated by the
solid line in FIG. 6 between the first stage fire time T1 of the
first stage inflator 9A and the desired second stage fire time T2
of the second stage inflator 9B.
In step 116, if it has been decided that
.vertline.G.vertline.<.vertline.G.sub.M.vertline. (stored data
G.sub.M is increased to the negative side much more than the
deceleration G being detected by the acceleration sensor 8), it is
then decided that the crash is not in the condition wherein fire of
the second stage inflator 9B is requested, and then the process
goes to step 128. In step 128, it is decided whether or not the
lapse time T from the first stage fire time T1 of the first stage
inflator 9A exceeds a predetermined period of time Ta.
Then, if it has been decided that the lapse time T exceeds the
predetermined period of time Ta (if YES), it is decided that the
crash has not come up to such extent that fire of the second stage
inflator 9B must be requested, and then the process is ended.
Conversely, if it has been decided that the lapse time T does not
exceed the predetermined period of time Ta (if NO), the process
advances to step 124A.
In this case, the predetermined period of time Ta is a time
interval between the first stage fire time T1 of the first stage
inflator 9A and the desired second stage fire time T2 of the second
stage inflator 9B.
On the contrary, in previous step 116, if it has been decided that
.vertline.G>.vertline.G.sub.M.vertline. (the deceleration G
being detected by the acceleration sensor 8 exceeds stored data
G.sub.M much more to the negative side), the threshold value VTH at
this point of time is held for a predetermined time and is used for
the predetermined time as a threshold value to decide whether or
not fire of the second stage inflator 9B is requested (see step 117
in FIG. 3).
More particularly, as described in step 108 in FIG. 3, first the
threshold value VTH is set based on the magnitude of the
deceleration G by using the preset relation and the previously
stored conversion table. Then, in this step 117, the threshold
value is calculated according to the deceleration G detected at
this point of time, and this value is held as the threshold value
VTH, which is employed to decide whether or not fire of the second
stage inflator 9B is requested, at its maximum until the desired
second stage fire time T2 of the second stage inflator 9B, whereby
the threshold value can be fixed.
In FIG. 7, a state of fixing the threshold value is shown
schematically. In FIG. 7, a point of time T3 is the point of time
when .vertline.G>.vertline.G.sub.M.vertline. is satisfied, and
the state is indicated by the chain double-dashed line wherein the
threshold value at this point of time is held and fixed up to the
desired second stage fire time T2 of the second stage inflator
9B.
After the threshold value has been fixed as above, it is decided
whether or not the lapse time T from the first stage fire time T1
of the first stage inflator 9A exceeds the predetermined period of
time Ta (see step 120 in FIG. 3). If it has been decided that the
lapse time T exceeds the predetermined period of time Ta (if YES),
the process is then terminated (see step 120 in FIG. 3).
In contrast, in step 120, if it has been decided that the lapse
time T does not exceed the predetermined period of time Ta (if NO),
it is decided whether or not the speed integral value .DELTA.V at
this point of time exceeds the threshold value V.sub.TH2, which is
set by fixing the threshold value in above step 117, to increase to
the negative side (.DELTA.V<V.sub.TH2) (see step 124A in FIG.
3).
Then, in step 124A, if it has been decided that
.DELTA.V<V.sub.TH2 is satisfied (if YES), i.e., if it has been
decided that the crash is in the state where fire of the second
stage inflator 9B is requested, the start signal is output from the
CPU 4 to the second stage inflator 9B via the D/A converter 6 and
the second interface circuit 7 and then the second stage inflator
9B is fired (see a point labeled by "Fire" in FIG. 7) (see step 126
in FIG. 3).
On the other hand, in step 124A, if it has been decided that
.DELTA.V<V.sub.TH2 is not satisfied (if NO), i.e. if it has been
decided that there is no need to fire the second stage inflator 9B,
the process returns to step 102. Then, a series of processes are
repeated newly.
In the above second embodiment, an integrating means can be
implemented by carrying out step 104 by the CPU 4, a first integral
value deciding means can be implemented by carrying out step 108 by
the CPU 4, an acceleration deciding means can be implemented by
carrying out step 116 by the CPU 4, a second integral value
deciding means can be implemented by carrying out steps 117, 120 by
the CPU 4, and a start signal outputting means can be implemented
by carrying out steps 110, 126 by the CPU 4.
In any of above embodiments, there has been made the explanation
such that the above start control can be effected under the premise
that the program for executing start control shown in FIG. 2 or
FIG. 3 is loaded previously onto the CPU 4. However, this program
does not have to be loaded previously onto the CPU 4. That is,
first the program is stored in the well known external recording
medium and then it may be loaded into the CPU 4 from the external
recording medium in execution of start control. As such external
recording medium, for example, there are a floppy disk, a hard
disk, a magnetic recording medium such as a magnetic tape, etc. Of
course, if such recording medium is employed, it is needless to say
that respective reading devices (a floppy disk drive, a hard disk
drive, etc.) must be provided.
In FIG. 8, an example of a configuration in case a floppy disk 10
is employed as the recording medium for recording the program is
shown. Loading of the program in case the floppy disk 10 is
employed as the recording medium will be explained with reference
to FIG. 8 hereunder.
A floppy disk drive 11 is connected to the CPU 4. The program is
recorded previously in the floppy disk 10. By operating the floppy
disk drive 11, the program is read from the floppy disk 10 and
loaded onto the CPU 4. Then, the program is ready for
execution.
As described above, according to the invention, there is considered
the fact that, under the situation that fire of both the first
stage inflator 9A and the second stage inflator 9B is needed but
stagnation of the speed integral value is caused after the first
stage inflator 9A has been fired, the deceleration derived after
fire of the first stage inflator 9A exceeds the maximum
deceleration produced in the type of crash which needs fire of the
first stage inflator 9A but not needs fire of the second stage
inflator 9B. Then, even if fire of both the first stage inflator 9A
and the second stage inflator 9B is needed but stagnation of the
speed integral value is caused after the first stage inflator 9A
has been fired, the second stage inflator 9B can be fired without
fail by adding the time integral value calculated over the area
where the deceleration exceeds the maximum deceleration to the
speed integral value in the prior art. As a result, start control
of the passenger protection system which has two-stage inflators
can be executed properly, so that the passenger protection system
with higher reliability than the prior art can be provided.
Since fire of the first stage inflator 9A is the necessary
condition for fire of the second stage inflator 9B, erroneous
inflation of the air bag caused in the clash which does not need
the inflation of the air bag or caused on the so-called rough road
can be prevented. As a result, the advantage that the reliability
can be improved further rather than the prior art can be
achieved.
As described above, according to the invention, there is considered
the fact that, under the situation that fire of both the first
stage inflator 9A and the second stage inflator 9B is needed but
stagnation of the speed integral value is caused after the first
stage inflator 9A has been fired, the deceleration derived after
fire of the first stage inflator 9A exceeds the maximum
deceleration produced in the type of crash which needs fire of the
first stage inflator 9A but not needs fire of the second stage
inflator 9B. Then, even if stagnation of the speed integral value
is caused after the first stage inflator 9A has been fired, the
second stage inflator 9B can be fired without fail by fixing the
threshold value, which is employed to decide the fire of the
inflators according to the deceleration, after a predetermined
point of time and then comparing the speed integral value with the
threshold value. As a result, start control of the passenger
protection system which has two-stage inflators can be executed
properly, so that the passenger protection system with higher
reliability than the prior art can be provided.
Since fire of the first stage inflator 9A is the necessary
condition for fire of the second stage inflator 9B, erroneous
inflation of the air bag caused in the crash which does not need
the inflation of the air bag or caused on the so-called rough road
can be prevented. As a result, the advantage that the reliability
can be improved further rather than the prior art can be
achieved.
* * * * *